Death from flu is generally uncommon, but new U.S. research has found that when children do die of the flu, it is likely that they have not been vaccinated.

Researchers with the U.S. Centers for Disease Control and Prevention recently completed a study in which they looked at 291 of the 358 U.S. children between ages 6 months to age 17 who died of the flu between 2010 and 2014.

They found that only 26 per cent of the children who died had been vaccinated against influenza.

In all, 153 of the children who died had underlying high-risk medical conditions, such as asthma, blood and endocrine disorders, or neurological problems. Even among them, only 31 per cent had been vaccinated.

Overall, the vaccine’s effectiveness against death was 65 per cent. The effectiveness of the vaccine among children with high-risk conditions was 51 per cent – a level of protection the study authors say is “significant.”

The study appears in this week’s issue of the journal Pediatrics.

The study authors conclude that the flu vaccine is linked to a reduced risk of flu-associated death among kids.

“This study highlights the importance of annual influenza vaccination for children, especially those with underlying high-risk medical conditions,” which they note puts children at higher risk of severe complications and influenza-associated death.